4a) Small amplitude oscillation as only valid for small angular amplitudes.

b) -Set up light string with Bob on the end,
attach top of string to clamp stand boss.
-Measure length from top to centre of Bob.
-Release the Bob so it oscillates with small amplitude.
-Use stop clock to measure time taken for 20 oscillations.
-Divide this by 20 for mean T
-Plot T^2 against L
-Calc Gradient
g=(4pi^2)/gradient
-Repeat procedure

c) -Student value 4x true value
-Time period half so all values for T^2 will be 1/4 the true
-Gradient is 4x lower
-State equation or show that g is inversely proportional to gradient.

5a) Lenz's Law: Direction of induced EMF/current is always in a direction that opposes the change that caused it.
Faraday's Law: Induced EMF is proportional to rate of change of flux linkage.

b) -Change in flux linkage when current flows.
-EMF induced in wheel (or whatever it was called)
-Current induced in the wheel as good conductor.
-Current carrying conductor (wheel) opposes the field due to coil, therefore there is a force against the direction of motion.

c) Wheel not in contact with electromagnet so no wear, but in brake pads there is wear due to friction.

More energy used or less effective or heating.

Either your 5a is wrong or the AQA text book is wrong. Because the text book says induced emf is EQUAL to rate of change of flux linkage. Not proportional. Plus if it was proportional then the equation would need a constant. But all the letters in the equation can be varied

(Original post by lucabrasi98)
Either your 5a is wrong or the AQA text book is wrong. Because the text book says induced emf is EQUAL to rate of change of flux linkage. Not proportional. Plus if it was proportional then the equation would need a constant. But all the letters in the equation can be varied

Both will be accepted as seen from previous mark schemes and there is a constant, that is -1.

4a) Small amplitude oscillation as only valid for small angular amplitudes.

b) -Set up light string with Bob on the end,
attach top of string to clamp stand boss.
-Measure length from top to centre of Bob.
-Release the Bob so it oscillates with small amplitude.
-Use stop clock to measure time taken for 20 oscillations.
-Divide this by 20 for mean T
-Plot T^2 against L
-Calc Gradient
g=(4pi^2)/gradient
-Repeat procedure

c) -Student value 4x true value
-Time period half so all values for T^2 will be 1/4 the true
-Gradient is 4x lower
-State equation or show that g is inversely proportional to gradient.

5a) Lenz's Law: Direction of induced EMF/current is always in a direction that opposes the change that caused it.
Faraday's Law: Induced EMF is proportional to rate of change of flux linkage.

b) -Change in flux linkage when current flows.
-EMF induced in wheel (or whatever it was called)
-Current induced in the wheel as good conductor.
-Current carrying conductor (wheel) opposes the field due to coil, therefore there is a force against the direction of motion.

c) Wheel not in contact with electromagnet so no wear, but in brake pads there is wear due to friction.

More energy used or less effective or heating.

For 5b, I put emf induced in coil by accident , I think the question was out of 3, would I get at least 1 for saying change in disk rotates, so change in flux ?

(Original post by DesignPredator)
Both will be accepted as seen from previous mark schemes and there is a constant, that is -1.

B,A,N and T can all be varied. A constant is something like G in the equation for gravitational firled strenth. The -1 isn't really a constant, it's just essentially demonstrating Lenz's law. It implies they're in opposite directions. And IIRC you had to mention lenz' law later in the question.

I don't recall any mark schemes where they accept both but maybe you're right

4a) Small amplitude oscillation as only valid for small angular amplitudes.

b) -Set up light string with Bob on the end,
attach top of string to clamp stand boss.
-Measure length from top to centre of Bob.
-Release the Bob so it oscillates with small amplitude.
-Use stop clock to measure time taken for 20 oscillations.
-Divide this by 20 for mean T
-Plot T^2 against L
-Calc Gradient
g=(4pi^2)/gradient
-Repeat procedure

c) -Student value 4x true value
-Time period half so all values for T^2 will be 1/4 the true
-Gradient is 4x lower
-State equation or show that g is inversely proportional to gradient.

5a) Lenz's Law: Direction of induced EMF/current is always in a direction that opposes the change that caused it.
Faraday's Law: Induced EMF is proportional to rate of change of flux linkage.

b) -Change in flux linkage when current flows.
-EMF induced in wheel (or whatever it was called)
-Current induced in the wheel as good conductor.
-Current carrying conductor (wheel) opposes the field due to coil, therefore there is a force against the direction of motion.

c) Wheel not in contact with electromagnet so no wear, but in brake pads there is wear due to friction.

More energy used or less effective or heating.

Cheers! I can't remember all my answers now but I recall getting a lot of similar answers. Do you remember what question 4(a) asked?